Ordovician-Silurian Extinction Event

The Ordovician-Silurian Extinction was the first of the 6 mass extinctions in earths history. It was the 3rd worst extinction, and wiped out 45-60% of all life, which was mostly marine at the time. This happened around 445-442 million years ago. Many marine animals disappeared, or were greatly declined after this event. Many arthropods went extinct, or were low in numbers. Trilobites suffered a 50% loss. Corals and early reefs, lost around 25-30% of their population as well. After the event, activity went down in the Silurian and Early Devonian.